1. Technical Field
This invention relates to the art of sensing operational defects in piston and bearing assemblies and, more particularly, to sensing such defects at sliding and rolling contact areas of an engine.
2. Discussion of the Prior Art
It is conventional in the automotive industry to test a newly assembled engine by a simple screening process to identify engine assemblies that bind. A torque transducer is placed between an engine assembly output member and a drive motor; the motor essentially drives the mechanical elements of the engine assembly in a nonfiring condition. This is a cummulative sensing technique because it is possible that some parts may be too loose and some too tight; the total torque may mask the problem of the overly tight parts which may be close to binding. This technique does not locate the source of friction causing defects, it merely renders a consensus that there may be a problem somewhere in the engine assembly without identifying the location. Additionally, such torque transducer tests may permit burrs to gouge out an annular groove on the first turn of the test, permitting the torque to go back down to normal without revealing a permanent defect. If any defect is discovered by the torque transducer test, the engine must be withdrawn from the assembly line, disassembled, and explored as to location of possible problems. This is time-consuming, not always accurate. If the friction causing defect has become permanent as a result of scratching or binding and has been discovered, this will eventually require rework or scraping of the sliding or rolling bearing surfaces. If the friction causing defect has not been discovered because permanent grooving has taken place, the engine in regular use may, depending on the location of the defect, experience knocking, loss of oil pressure, seizure of crankshaft, or premature engine failure. To fix such defect in the field may cost 40 times what it would cost to fix the defect at the assembly line.
Similarly, dynamometer devices which sense an accumulation of delicate engine parameters while the engine is running hot are not useful to screen out friction causing defects because the sensing will be too late after damage has become permanent (see U.S. Pat. No. 3,592,053).
It would be desirable if dimensional or friction generating defects in newly assembled engines could be sensed by a technique that locates the defect in an extremely short time period, before the defect can damage the sliding or rolling surfaces and particularly before a friction binding part can penetrate the assembly oil film at such contact areas. It would further be desirable if radiation from such dimensional defects could be sensed sufficiently quickly and accurately to determine location and type of such defects before such damage can occur.
Heat sensors, such as those permanently incorporated, in a rotary engine (see U.S. Pat. No. 3,886,912), or valve body (see U.S. Pat. No. 3,921,435) to sense binding, are inappropriate for detection use in multiple bearing or piston assemblies such as a complex internal combustion engine; a large number of sensors, such as 15 or more, would have to be incorporated, increasing the cost and complexity.
Infrared radiation cameras have been used to monitor the heat pattern, on a gross or macroscale, of large storage tanks or containers, such heat pattern having been in existence for some time at a desirably constant level. A change in the heat pattern would signal the possibility of a lining breakthrough (see U.S. Pat. Nos. 4,343,182 and 3,596,519). Unfortunately, the use of radiation cameras in this limited manner is not adaptable to engine analysis since there is no preexisting heat pattern but only a small amount of heat that may be generated by the initial, but very limited, time period for motoring the engine assembly and before damage can occur to the sliding or rolling surfaces and particularly before damage can occur as a result of penetrating the assembly oil film present throughout the engine. Such time period is less than 15 seconds.